Voltage monitoring system and voltage monitoring module

ABSTRACT

In a voltage monitoring system, a voltage monitoring module includes an adjusting current control circuit to generate an adjusting current so that the operating current consumed by the voltage monitoring modules reaches a specified value corresponding to a first operation current setting command, and stops generating the adjusting current according to an operating current switching command; and an operating current measurement circuit to measure the operating current according to the operating current measuring command following the operating current switching command; and in which a module control circuit sends a second operation current setting command based on the operating current that was measured, and the adjusting current control circuit generates an adjusting current so that the operating current reaches a specified value corresponding to the second operating current setting command.

CROSS-REFERENCE TO RELATED APPLICATIONS

The disclosure of Japanese Patent Application No. 2011-122094 filed onMay 31, 2011 including the specifications, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND

The present invention relates to a voltage monitoring system and voltagemonitoring module and relates in particular to a voltage monitoringsystem and voltage monitoring module to monitor the voltage of cells ina battery pack utilizing multiple cells coupled in series as one batterycell.

In recent years, battery cells that supply electrical power to themotors such as in automobiles often use battery packs that are multiplecells coupled in series as one battery cell. An equal voltage must bemaintained in the cells in order to maintain performance in this batterypack. Numerous voltage monitoring systems have therefore been proposedfor monitoring the voltage in each of the battery cells that form thebattery pack.

In the voltage monitoring systems, one voltage monitoring module isinstalled for multiple battery cells, and multiple voltage monitoringmodules monitor the voltage of all cells in the battery pack. Thevoltage monitoring modules operate at this time from power supplied fromthe battery cell group for monitoring. Therefore, when a difference inelectrical current consumption occurs among the voltage monitoringmodules in the voltage monitoring system, then a difference in batterycell electrical current consumption speed occurs between a battery cellgroup monitored by one voltage monitoring module, and the battery cellgroups monitored by the other voltage monitoring modules. Thisdifference in electrical current consumption speeds causes a differencein voltage among the battery cells, creating the problem of a drop inbattery pack performance.

Japanese Unexamined Patent Application Publication No. 2010-81692therefore discloses a technology for equalizing the current consumptionin multiple voltage monitoring modules. Japanese Unexamined PatentApplication Publication No. 2010-81692 is technology relating to avehicular power supply monitoring device. FIG. 17 shows a block diagramof the vehicular power supply device disclosed in Japanese UnexaminedPatent Application Publication No. 2010-81692. The vehicular powersupply device shown in FIG. 17 includes a drive battery 101 includingmultiple battery cells 103 coupled in series to supply electrical powerto the motor driving the vehicle; and multiple sensing circuits 105 toisolate the drive battery 101 into multiple cell blocks 102 and detectthe state in each of the separate cell blocks 102. Each of these sensingcircuits 105 operates from power supplied from each of the cell blocks102. Moreover, an equalizing circuit 110 for equalizing each of the cellblock 102 load currents to a specified current value is coupled to eachof the sensing circuits 105. This equalizing circuit 110 equalizes theload current in each of the cell blocks 102 per the operating state ofeach sensing circuit 105.

FIG. 18 shows a block diagram of the equalizing circuit 110 disclosed inJapanese Unexamined Patent Application Publication No. 2010-81692. Theequalizing circuit 110 in FIG. 18 increases or decreases the balancecurrent flowing in the balance current adjusting circuit 113 accordingto the increase or decrease in the voltage differential occurring acrossboth ends of the current detector resistor 112 according to theelectrical current (consumption current) flowing in the current detectorresistor 112. More specifically, the balance current adjusting circuit113 increases or decreases the balance current flowing in the outputtransistor 117 based on the voltage differential between the referencevoltage 115 and the amplified voltage output from the differentialamplifier 114 amplifying the voltage differential occurring across bothends of the current detector resistor 112. The balance current at thistime lowers if the voltage differential across both ends of the currentdetector resistor 112 increased, and rises if the voltage differentialacross both ends of the current detector resistor 112 has decreased. Thesize of the balance current can be set by varying the reference voltage115. The current setting adjusting circuit 120 varies the voltage valueof the reference voltage 115.

The vehicular power supply device disclosed in Japanese UnexaminedPatent Application Publication No. 2010-81692 in other words equalizesthe consumption current among the sensing circuits 105 by setting thereference voltage 115 so that the consumption current flowing in each ofthe sensing circuits 105 is the same or larger than the largestconsumption, current among the consumption current flowing among thesensing circuits 105.

SUMMARY

Electrical current consumption in the battery cell monitoring modulesmust be lowered in order to limit current consumption in the batterypack cells. Normally there is no need to constantly monitor the voltagesin the battery cells since intermittent voltage monitoring issufficient. One method to reduce the electrical current consumption isto apply the sleep mode to stop voltage monitoring operation of thebattery cell by the voltage monitoring module. The load current in thecells therefore changes according to whether the battery cell monitoringmodule is operating either in normal mode for voltage monitoringoperation or for sleep mode to stop voltage monitoring operation.Moreover, the load current in the battery cell will change each momentaccording to the vehicle drive state, even if operating in the samemonitoring mode.

Since the load current in the battery cell fluctuates in this wayaccording to the operating mode and the vehicle drive state, extendingthe life of the cells in the battery pack requires resetting the currentconsumption values of the voltage monitoring module to an ideal value,according to the fluctuations in the operating mode and the vehicledrive state.

However, an optimal value cannot be set in the power supply devicedisclosed in Japanese Unexamined Patent Application Publication No.2010-81692 when resetting current consumption values that are jointlyused by all the voltage monitoring modules. Setting an optimal value isimpossible because the common current consumption value for allmonitoring modules is set based on each measured value found frommeasuring the current consumed by each monitoring module but thismeasured value includes a balance current portion for equalizing theconsumption current and so this value does not reflect the actualcurrent consumed in each monitoring module. In other words, the powersupply device disclosed in Japanese Unexamined Patent ApplicationPublication No. 2010-81692 is not able to set an optimal value whenresetting the common current consumption value for all voltage modules.This method cannot therefore reset an ideal current consumption valueaccording to fluctuations in the operating mode or vehicle drive state.Moreover, since the technology in Japanese Unexamined Patent ApplicationPublication No. 2010-81692 cannot reset each IC's current consumptionvalue, the discharge characteristic in each battery cell will remaindifferent because there is no optimal value for equalization, causingthe problem of a drop in the life of the battery pack.

According to one aspect of the present invention, a voltage monitoringsystem is a system for monitoring multiple battery cells mutuallycoupled in series and includes a voltage monitoring module for operatingon a voltage received from at least one battery cell among multiplebattery cells and monitoring the battery cells, and a module controlcircuit for controlling the voltage monitoring module; and the voltagemonitoring module includes an adjusting current control circuit thatgenerates an adjusting current in response to a first operating currentsetting command sent from the module control circuit so that anoperating current consumed by the voltage monitoring module reaches aspecified value corresponding to the first operating current settingcommand and stops generating of the adjusting current in response to anoperating current switching command sent from the module controlcircuit; and an operating current measurement circuit that measures theoperating current in response to an operating current measuring commandsent following the operating current switching command from the modulecontrol circuit, in which the module control circuit sends a secondoperating current setting command based on the measured operatingcurrent, and the adjusting current control circuit generates anadjusting current in response to the second operating current settingcommand so that the operating current reaches a specified valuecorresponding to the second operating current setting command.

According to another aspect of the present invention, a voltagemonitoring module operates on a voltage received from at least onebattery cell among multiple battery cells mutually coupled in series andmonitors the battery cells, and includes an adjusting current controlcircuit that generates an adjusting current in response to a firstoperating current setting command sent from the external section so thatan operating current consumed by the voltage monitoring module reaches aspecified value corresponding to the first operating current settingcommand and stops generating of the adjusting current according to anoperating current switching command sent from an external section; andan operating current measurement circuit that measures the operatingcurrent according to the operating current measuring command sentfollowing the operating current switching command from an externalsection; and the adjusting current control circuit generates anadjusting current in response to a second operating current settingcommand that was generated based on the measured operating current sothat the operating current reaches a specified value corresponding tothe second operating current setting command.

According to the aspects of the present invention, the voltagemonitoring system and voltage monitoring module stops the adjustingcurrent generated in the adjusting current control circuit and measuresthe operating current according to an operating current measuringcommand sent following the operating current switching command. Theadjusting current control circuit then generates an adjusting current inresponse to a second operating current setting command generated basedon the measured operating current so as to attain a specified valuecorresponding to the second operating current setting command. In otherwords, the voltage monitoring system and voltage monitoring moduleaccording to the present invention is capable of rewriting or updatingthe size of the adjusting current to match the state of the voltagemonitoring module.

According to the aspects of the present invention, the voltagemonitoring system and voltage monitoring module is capable of rewritingthe consumption current of the voltage monitoring module to match thestate of the voltage monitoring module.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of the motor drive device including thevoltage monitoring system of the present invention;

FIG. 2 is a block diagram of the voltage monitoring system of thepresent invention;

FIG. 3 is a block diagram of the voltage monitoring module of thepresent invention;

FIG. 4 is a block diagram of the voltage monitoring module of the firstembodiment;

FIG. 5 is a block diagram of the adjusting current control circuit andthe regulator unit for the power supply circuit of the first embodiment;

FIG. 6 is a block diagram of the current setting resistor of the firstembodiment;

FIG. 7 is a graph showing the current output characteristics of theadjusting current control circuit and the regulator unit for the powersupply circuit of the first embodiment;

FIG. 8 is a block diagram of the cell monitor unit of the firstembodiment;

FIG. 9 is a sequence diagram showing the procedure for setting theoperating current during normal operation mode in the voltage monitorsystem of the first embodiment;

FIG. 10 is a sequence diagram showing the procedure for updating theoperating current in the voltage monitoring system of the firstembodiment;

FIG. 11 is a table for describing the operating current during normaloperating mode in the voltage monitoring module in the voltagemonitoring system in the first embodiment;

FIG. 12 is a sequence diagram showing the procedure for shifting tosleep mode from normal operating mode in the voltage monitoring systemof the first embodiment;

FIG. 13 is a table for describing the operating current during sleepmode in the voltage monitoring module of the voltage monitoring systemof the first embodiment;

FIG. 14 is a sequence diagram showing the procedure for shifting tonormal operating mode from sleep mode in the voltage monitoring systemof the first embodiment;

FIG. 15 is a block diagram of the adjusting current control circuit andthe regulator unit for the power supply circuit of the secondembodiment;

FIG. 16 is a block diagram of the motor drive circuit including thevoltage monitoring system of the third embodiment;

FIG. 17 is a block diagram of the vehicular power supply devicedescribed in Japanese Unexamined Patent Application Publication No.2010-81692; and

FIG. 18 is a block diagram of the current adjusting circuit described inJapanese Unexamined Patent Application Publication No. 2010-81692.

DETAILED DESCRIPTION

First Embodiment

The embodiments of the present invention are described next whilereferring to the drawings. In the drawings, the same reference numeralsare attached to the same element, and redundant sections are omittedwhere not required.

The voltage monitoring system for monitoring the output voltage of thebattery pack supplying power for example to an electric vehicle isdescribed next assuming an understanding of the embodiment of thepresent invention is required. An overview of the voltage monitoringsystem VMS for monitoring the output voltage of the battery packsupplying power for example to an electric vehicle is first of alldescribed while referring to FIG. 1. FIG. 1 is a block diagram showingthe structure of the voltage monitoring system VMS for monitoring theoutput voltage of the battery pack supplying power to an electricvehicle, etc. The voltage monitoring system VMS includes the voltagemonitoring modules VMM1 through VMMn (n is an integer of 2 or more), aninsulation element INS1 and INS2, a cell monitoring unit CMU, and abattery management unit BMU. The cell monitoring unit CMU and thebattery management unit BMU are comprised for example from amicrocomputer (hereafter, MCU: Micro Computing Unit).

The voltage monitoring system VMS monitors the voltage of the batterypack assembly by way of the voltage monitoring modules VMM1-VMMn. Thebattery pack assembly includes n number of the cell modules EM1-EMncoupled in series. Each of the cell modules EM1-EMn includes m number ofserially coupled battery cells (m is an integer of 2 or more). Thebattery pack assembly is in other words, (m×n) number of seriallycoupled battery cells. The battery pack assembly can in this way achievea high output voltage.

The cell monitoring unit CMU is coupled by way of the insulation elementINS2 to the communication input terminal of the voltage monitoringmodules VMMn, and coupled by way of the insulation element INS1 to thecommunication output terminal of the voltage monitoring module VMM1.Components such as photocouplers are utilized as the insulation elementsINS1 and INS2, and electrically isolate the voltage monitoring modulesVMM1-VMMn from the cell monitoring unit CMU. The cell monitoring unitCMU can in this way be protected from damage in the event of a breakdownor similar problem from high voltage applied from the battery packassembly to the cell monitoring unit CMU.

The cell monitoring unit CMU is further coupled to the batterymanagement unit BMU. The cell monitoring unit CMU calculates the outputvoltage of each battery cell from the voltage monitoring results fromthe voltage monitoring modules VMM1 through VMMn and reports theseresults to the battery management unit BMU. The cell monitoring unit CMUalso controls the operation of voltage monitoring modules VMM1-VMMnaccording to commands from the battery management unit BMU. The batterymanagement unit BMU is further coupled to the engine control unit (ECU).The battery management unit BMU controls the voltage monitoring systemVMS operation according to commands from the engine control unit ECU andthe output voltage from each battery cell reported from the cell monitorunit. The battery management unit BMU notifies the engine control unitECU of information such as relating to the status of the battery packassembly and the voltage monitoring system VMS. The operation of thecell monitoring unit CMU and the battery management unit BMU isdescribed in detail in the voltage monitoring system VMS described lateron.

The coupling between the voltage monitoring modules VMM1-VMMn and thecell monitoring unit CMU is described next while referring to FIG. 2.Here, FIG. 2 is a block diagram of an essential section of the voltagemonitoring system VMS showing the connection relation between thevoltage monitoring modules VMM1-VMMn and the cell monitoring unit CMU.The voltage monitoring modules VMM1-VMMn are coupled to the respectivecell modules EM1-EMn, and monitor the voltages received from the cellmodules EM1-EMn. The voltage monitoring modules VMM1-VMMn are in a daisychain configuration, and the output from the communication circuit forthe voltage monitoring modules VMM2-VMMn is coupled to the respectivecommunication circuit input of the voltage monitoring modules VMM1-VMM(n−1).

The cell monitoring unit CMU outputs a control signal by way of theinsulation element INS2 to the voltage monitoring modules VMMn. Thecontrol signals for the voltage monitoring modules VMM1-VMM (n−1) areconveyed by utilizing a daisy chain configuration to the voltagemonitoring modules VMM1-VMMn (n−1). The cell monitoring unit CMU in thisway controls the operation of the voltage monitoring modules VMM1-VMMn.The voltage monitoring modules VMM1-VMMn output the monitoring resultsby way of the insulation element INS1 to the cell monitoring unit CMUaccording to control signals received from the cell monitoring unit CMU.The monitoring results from the voltage monitoring modules VMM2-VMMn areconveyed to the cell monitoring unit CMU by utilizing a daisy chainconfiguration.

The respective configurations of each of the voltage monitoring modulesVMM1-VMMn are described next. The voltage monitoring modules VMM1-VMMneach possess the same configuration. The configuration of the voltagemonitoring modules VMM1 is described as a typical example whilereferring to FIG. 3. FIG. 3 is a block diagram showing the configurationof the voltage monitoring module VMM1. The voltage monitoring moduleVMM1 includes a power supply circuit VMM_S, a communication circuitVMM_C, a voltage measurement circuit VMC, a cell balance circuitsCB1-CBm (m is an integer of 2 or more), the power supply terminal VCC,the input terminals V1-V (m+1), the cell balance input terminalsVB1-VBm, communication input terminal Tin and the communication outputterminal Tout.

In the cell module EM1, the battery cells EC1-ECm are serially connectedin order from the high voltage side. In the voltage monitoring moduleVMM1, the power supply terminal is coupled to the high voltage side ofthe battery cell EC1. The low voltage side of the battery cell ECm iscoupled to the input terminal V (m+1). Voltage at the input terminalbranches within the voltage monitoring module VMM1 and is supplied tothe voltage measurement circuit VMC and the communication circuit VMM_Cas a ground voltage. The output voltage from the cell module EM1 is inthis way supplied as a power supply voltage to the voltage monitoringmodule VMM1. The power supply circuit VMM_S receives power by way of thepower supply terminal VCC from the battery cell EC1. The power supplycircuit VMM_S supplies power to the communication circuit VMM_C and thevoltage measurement circuit VMC.

The voltage measurement circuit VMC includes a selector circuit VMC_SEL,A/D converter (Analog to Digital Converter: ADC) VMC_ADC, registerVMC_REG and control circuit VMC_CON. The selector circuit VMC_SELincludes the switch SWa_1 through SWa_m and SWb_1 through SWb_m. Theswitches SWa_1 through SWa_m and SWb_1 through SWb_m are turned on andoff by control signal from the control circuit VMC_CON. Here, theswitches SWa_j and SWb_j turn on simultaneously, when j is set as aninteger from 1 through m and when measuring the voltage of the batterycell ECj. The voltage from the high voltage side terminal of batterycell ECj is in this way supplied by way of the input terminal Vj, as thehigh voltage side voltage VH to the A/D converter VMC_ADC. The voltagefrom the low voltage side terminal of battery cell ECj is in the sameway supplied by way of the input terminal V (j+1) as the low voltageside voltage VL to the A/D converter VMC_ADC.

The A/D converter VMC_ADC converts the high voltage side voltage VH andthe low voltage side voltage VL to digital values serving as the voltagevalues. The A/D converter VMC_ADC then outputs those voltage valuesserving as the digital values to the register VMC_REG. The registerVMC_REG stores the voltage values output from the A/D converter VMC_ADC.The control circuit repeats the operation for sequentially setting theswitches SWa_1 through SWa_m and SWb_1 through SWb_m to on state, ateach specified time (for example, 10 msec). The control circuit in thisway overwrites the voltage values supplied to the input terminal Vj andV(j+1) into the register VMC_REG at each specified time.

The communication circuit VMM_C receives the command from the cellmonitoring unit CMU and the outputs from the other voltage monitoringmodules VMM2-VMMn by way of the communication input terminal Tin. Thecommunication circuit VMM_C then transfers the command from the cellmonitoring unit CMU to the control circuit VMC_CON. The communicationcircuit VMM_C then transfers the output from the voltage monitoringmodules VMM2-VMMn unchanged to the cell monitoring unit CMU.

The cell balance circuit CBj and the externally mounted resistor Rj areexternally coupled between the respective input terminals Vj and theinput terminals (j+1) by way of the cell balance input terminal VBj. Thesetting of the cell balance circuit CBj to the on state causes currentflow between the input terminal Vj and the input terminal V(j+1). The onand off control of the cell balance circuits CB1-CBm by the controlcircuit VMC_CON causes selective discharging of the battery cellsEC1-ECm.

The operation of the voltage monitoring system VMS is described nextwhile referring to FIG. 1. The battery cell output voltage monitoringoperation is first of all described. The voltage monitoring system VMSstarts the battery cell output voltage monitoring operation according tothe voltage monitoring operation start command from the cell monitoringunit CMU. The engine control unit ECU for example detects the power-onstate in the electric vehicle, and issues a voltage monitoring systemVMS startup command to the battery management unit BMU. The batterymanagement unit BMU issues a voltage monitoring modules VMM1-VMMnstartup command to the cell monitoring unit CMU according to the voltagemonitoring system VMS startup command. The cell monitoring unit CMUissues a voltage monitoring operation start command to the voltagemonitoring modules VMM1-VMMn according to the voltage monitoring modulesVMM1-VMMn.

The operation of the voltage monitoring modules VMM1-VMMn is describedwhile referring to FIG. 3. The voltage monitoring modules VMM1-VMMn thatreceived the voltage monitoring operation start command each perform thesame operation so the operation of the voltage monitoring module VMM1 isdescribed hereafter as a representative example. The voltage monitoringmodule VMM1 starts the voltage monitoring operation according to thevoltage monitoring operation start command from the cell monitoring unitCMU. More specifically, the communication circuit VMM_C transfers thevoltage monitoring operation start command from the cell monitoring unitCMU to the control circuit VMC_CON of the voltage measurement circuitVMC. The control circuit VMC_CON sets the switches SWa_j and SWb_j tothe on state according to the voltage monitoring operation startcommand. The input terminals Vj and V(j+1) are in this way coupled tothe respective A/D converter VMC_ADC. The A/D converter VMC_ADC convertsthe size of the voltages supplied to the coupled input terminals Vj andV(j+1) to digital values serving as the voltage values, and writes thevoltage values into the register VMC_REG.

In this example, the control circuit VMC_CON sequentially sets theswitches SWa_1-SWa_m and SWb_1-SWb_m to the on state within a specifiedtime. Namely, the control circuit VMC_CON repeats m number of switchingoperations within a specified time. The specified amount of time is forexample 10 milliseconds. In this case, the voltage monitoring moduleVMM1 measures the value of the voltages respectively supplied to theinput terminals Vj and V(j+1) at each specified time (10 msec) andsuccessively overwrites those measured values into the register VMC_REG.The voltage monitoring module VMM1 continues the above described voltagemonitoring operation unless there is a command from the cell monitoringunit CMU.

When search for a battery cell output voltage value for controlling theelectric vehicle, the cell monitoring unit CMU issues a voltage outputcommand to the voltage monitoring module VMM1 according to the commandreceived from the battery management unit BMU. The voltage monitoringmodule VMM1 outputs the voltage value of the specified input terminal tothe cell monitoring unit CMU according to the voltage value outputcommand. More specifically, the communication circuit VMM_C transfersthe voltage value output command from the cell monitoring unit CMU tothe control circuit VMC_CON of the voltage measurement circuit VMC. Thecontrol circuit VMC_CON issues an output command to the register VMC_REGaccording to the voltage value output command. The control circuitVMC_CON in this case specifies which of the input terminal voltagevalues to output to the register VMC_REG. The register VMC_REG outputsthe voltage value of that specified input terminal by way of thecommunication circuit VMM_C to the cell monitoring unit CMU at the timethat the output command is received according to the output command fromthe control circuit VMC_CON.

The cell monitoring unit CMU calculates the output voltage of thebattery cell ECj from the voltage values for the input terminals Vj andV(j+1) received from the voltage monitor module VMM1. The cellmonitoring unit CMU can for example calculate the output voltage of thebattery cell EC1 from the voltage differential between the inputterminal V1 and the input terminal V2. The cell monitoring unit CMU thennotifies the battery management unit BMU of the calculated battery celloutput voltage according to the request from the battery management unitBMU.

When the electric vehicle is in the power-off state, the engine controlunit ECU detects the power-off stage in the electric vehicle and issuesa stop command for the voltage monitoring system VMS to the batterymanagement unit BMU. The battery management unit BMU issues a stopcommand for the voltage monitoring modules VMM1-VMMn to the cellmonitoring unit CMU according to the stop command for the voltagemonitoring system VMS. The cell monitoring unit CMU issues a voltagemonitoring operation stop command to the voltage monitoring modulesVMM1-VMMn according to the stop command for the voltage monitoringmodules VMM1-VMMn. The voltage monitoring modules VMM1 stops the voltagemonitoring operation according to the voltage monitoring operation stopcommand from the cell monitoring unit CMU. More specifically, thecommunication circuit VMM_C transfers the voltage monitoring operationstop command from the cell monitoring unit CMU to the control circuitVMC_CON of the voltage measurement circuit VMC. The control circuitVMC_CON sets all the switches SWa_1-SWa_m and SWb_1-SWb_m to the offstate according to the voltage monitoring operation stop command. Thevoltage monitoring operation is stopped in this way.

The voltage monitoring operation of the battery cells was describedabove. However, the voltage monitoring system VMS is mounted for examplein electric vehicles and so must operate under electric vehicle usageconditions. Operation of the voltage monitoring system VMS according toelectric vehicle usage conditions is therefore described next.

Continued usage of electric vehicles requires electrically charging thebattery pack assembly by an electric charging unit, etc. In order tocharge the battery pack assembly, the engine control unit ECU detects anoperation by the driver such as coupling the charging plug, and issues acharging command to the battery management unit BMU in order to chargethe battery pack assembly. The battery management unit BMU opens therelays REL1 and REL2 according to the charging command from the enginecontrol unit ECU. This operation electrically cuts off the battery packassembly and the inverter INV. The battery pack assembly is charged inthis way by supplying an external charging voltage CHARGE to the batterypack assembly by way of the charging plug, etc.

Overcharging or over discharging of rechargeable batteries such asbattery cells is generally known to shorten the battery cell life.Moreover, in structures such as battery pack assemblies where multiplebattery cells are coupled in series, variations or irregularities suchas during battery cell production cause voltage irregularities to occureven in the same charging and discharging operation. Repeating thecharging operation on the battery pack assembly while theseirregularities are still occurring causes deterioration just in aparticular battery cell and also overcharging and over-discharging tooccur. The overcharging and over-discharging therefore shortens the lifeof the overall battery pack assembly and causes breakdowns to occur.Utilizing serially coupled battery cells therefore requires maintaininga voltage balance (so-called cell balance) in each battery cell.

The battery cell operation in the voltage monitoring system VMS whencharging this electric charging unit and so on is described next.Methods for calculating the output voltage of the cell and outputvoltage monitoring operation of the battery cell are the same as alreadydescribed and so are omitted here.

First of all, the battery management unit BMU issues an output voltagemeasuring command to the cell monitoring unit CMU according to thecharging command from the engine control unit ECU. The cell monitoringunit CMU calculates the output voltage for all the battery cells in thebattery pack assembly according to the output voltage measuring commandfrom the battery management unit BMU and notifies the battery managementunit BMU of the calculated output voltages. The battery management unitBMU designates the battery cell with the lowest output voltage withinthe battery pack assembly. In order to simplify the description here,the battery cell EC1 in the cell module EM1 serves as the battery cellwith the lowest output voltage within the battery pack assembly.

The battery management unit BMU then issues a cell balance operatingcommand to the cell monitoring unit CMU. The cell monitoring unit CMUissues a discharge command to the voltage monitoring modules VMM1-VMMnaccording to the cell balance operating command. The operation of thevoltage monitoring module VMM1 is next described as a representativeexample. In the voltage monitoring module VMM1, the control circuitVMC_CON in the voltage measurement circuit VMC receives a dischargecommand by way of the communication circuit VMM_C. The control circuitVMC_CON sets the cell balance circuits CB2-CBm to the on state accordingto the discharge command and in this way discharges the battery cellsEC2-ECm.

The cell monitoring unit CMU calculates the output voltages of thebattery cells EC2-ECm one after another during discharge. Then if any ofthe output voltages among the battery cells has dropped to the outputvoltage of battery cell EC1, then a discharge stop command is issued tostop the discharge operation in the applicable battery cell. Thefollowing description is for describing the case where the outputvoltage of battery cell EC2 was lowered to the output voltage of batterycell EC1 by discharging. First of all, the cell monitoring unit CMUdetects a drop in the output voltage of battery cell E2 down to theoutput voltage of battery cell EC1. The cell monitoring unit CMU thenissues a discharge stop command for the battery cell EC2 to the voltagemonitor module VMM1.

The control circuit VMC_CON of voltage monitoring module VMM1 receivesthe discharge stop command for the battery cell EC2 by way of thecommunication circuit VMM_C. The control circuit VMC_CON sets the cellbalance circuit CB2 to the off state according to the discharge stopcommand for the battery cell EC2. The control circuit VMC_CON in thisway stops discharging of the battery cell EC2, and the output voltage ofbattery cell EC2 attains the same output voltage as the battery cellEC1. The cell monitoring unit CMU performs this same operation to makethe output voltage of each cell among the battery cells EC3-ECM of cellmodule EM1 and cell modules EM2-EMn attain the same output voltage asthe battery cell EC1. The output voltage in each battery cell of thecell modules EM2-EMn are in this way made uniform (equalized) and thecell monitoring unit CMU terminates the cell balance operation. The cellmonitoring unit CMU notifies the battery management unit BMU that thecell balance operation has ended.

The battery management unit BMU issues a charge start command to thecharging section (not shown in drawing) coupled to the charging plug,according to the cell balance operation termination notification. Anexternal charging voltage CHARGE is in this way supplied to the batterypack assembly, and charging of the battery pack assembly begins.

The cell monitoring unit CMU monitors the output voltage of each cellduring charging. Then, if any of the battery cell output voltages hasreached the charging upper limit voltage, an overcharge warning noticeis conveyed to the battery management unit BMU. The battery managementunit BMU issues a charge stop command to the charging section accordingto the overcharge warning notification. The supply of the externalcharging voltage CHARGE is in this way cut off and the charging stops.The charging, upper limit voltage is preferably set to a voltage smallerthan the threshold voltage level during charging, so that charging upperlimit voltage will include an ample (safety) margin from the voltagelevel during overcharging in order to allow reliably preventing anovercharge of the battery cell from occurring.

There are irregularities among the charging characteristics of eachbattery cell among the cell module EM1-EMn. Consequently irregularitiesoccur in each of the battery cell voltage value after charging. The cellmonitoring unit CMU therefore measures the output voltage of eachbattery cell in order to determine the voltage value irregularities ineach battery cell. The cell monitoring unit CMU judges whether theoutput voltage irregularities from each battery cell are within aspecified range. The cell monitoring unit then notifies the batterymanagement unit BMU of the judgment results.

If the output voltage irregularities from each battery cell are notwithin the specified range then the battery management unit BMU commandsthe cell monitoring unit CMU to start the cell balance operation. Aftercompletion of the cell balance operation, the battery management unitBMU commands that charging start in the charging section. On the otherhand, if output voltage irregularities from each battery cell are withinthe specified range, then the battery management unit BMU notifies theengine control unit ECU that charging is now complete. The enginecontrol unit ECU displays the information that charging of the batterypack assembly was completed on a display device mounted at the driver'sseat. By monitoring the battery cell output voltages as described above,the voltage monitoring system VMS can prevent overcharging and alsocharge the battery pack assembly to a fully charged state whilemaintaining a satisfactory cell balance.

Making the electric vehicle accelerate is described next. To make theelectric vehicle accelerate, the engine control unit ECU detects forexample the driver depressing the accelerator pedal and issues anaccelerator command to the inverter INV and the battery management unitBMU to make the electric vehicle accelerate. The inverter INV switchesthe operating mode to direct current-to-alternate current conversionmode according to the accelerator command from the engine control unitECU. The battery management unit BMU closes the relays REL1 and REL2according to the accelerator command from the engine control unit ECU.The battery pack assembly in this way supplies a direct current (DC)voltage to the inverter INV. The inverter INV converts the DC voltage toan AC (alternate current) voltage and supplies the AC current to themotor-generator MG. The motor-generator MG generates a driving force byreceiving the supplied AC (alternate current) voltage. The driving forcegenerated in the motor-generator MG is conveyed to the (vehicle) drivewheels by the driveshaft or other mechanism to make the electric vehicleaccelerate.

Making the electric vehicle accelerate consumes the electric poweraccumulated in the battery cell and the battery cell output voltagecontinuously drops. A measure is therefore required to preventover-discharging the battery cells. The voltage monitoring system VMStherefore continuously monitors the output voltages from the batterycells during driving of the vehicle. In the case for example that any ofthe battery cell voltages fall below the warning level voltage, then thecell monitoring unit CMU issues a voltage drop warning to the batterymanagement-unit BMU. The battery management unit BMU issues a batterypack assembly low remaining charge warning to the engine control unitECU. The engine control unit ECU displays the battery pack assembly lowremaining charge warning on the display device mounted at the driver'sseat to notify the driver that over-discharging might be occurring inthe battery cells. The voltage monitoring system VMS can in this wayurge the driver to take measures to prevent over-discharging such as bystopping the vehicle, etc.

If the vehicle continues to be driven even after the battery packassembly low remaining charge warning, then the output voltage from thebattery cells will drop even further. So to prevent excessive batterycell discharging, the discharge within each battery cell must thereforebe stopped. In case for example that the voltage in any of the batterycells has fallen to the emergency shutdown level then the cellmonitoring unit CMU issues an emergency shutdown warning to the batterymanagement unit BMU. The emergency stop level voltage is preferably setto a voltage larger than the over-discharge threshold voltage level, andso includes an ample (safety) margin above the over-discharge voltagelevel in order to reliably prevent over-discharge from occurring in thebattery cells.

The battery management unit BMU starts the emergency stop operationaccording to the emergency stop warning from the cell monitoring unitCMU. More specifically, the battery management unit BMU opens the relayREL1 and REL2 to cut off the supply of power from the battery packassembly to the inverter INV. This action stops the drop in outputvoltage from the battery cells. The battery management unit BMU alsonotifies the engine control unit ECU that the emergency stop operationwas executed. The engine control unit ECU displays an indication showingthat the emergency stop operation was initiated on a display devicemounted at the driver's seat. The occurrence of battery cellover-discharging is reliably prevented in this way.

The operation when decelerating the electric vehicle is described next.When making the electric vehicle decelerate, the engine control unit ECUdetects for example the driver depressing the brake pedal and issues adecelerator command to the inverter INV and the battery management unitBMU to decelerate the electric vehicle. The inverter INV switches theoperating mode to alternate current-to-direct current conversion modeaccording to the decelerator command from the engine control unit ECU.The battery management unit BMU closes the relays REL1 and REL2according to the decelerator command from the engine control unit ECU.The motor-generator MG generates electricity from the rotational forceof the tires conveyed by way of the driveshaft, etc. The rotationalresistance occurring from the generation of electricity is conveyed byway of the drive shaft to the drive wheels as a braking force. Theelectric vehicle is in this way made to decelerate. The braking methodis generally given the name regenerative braking operation. Thealternate current (AC) voltage generated by this regenerative brakingoperation is supplied to the inverter INV. The inverter INV converts thealternate current (AC) voltage from the motor-generator MG to a directcurrent (DC) voltage and supplies this DC voltage to the battery packassembly. The battery pack assembly in this way performs charging fromvoltage recovered in the regenerative braking operation.

The regenerative braking operation charges the battery pack assembly sothat the output voltage of each battery cell rises. Some measure musttherefore be implemented to prevent overcharging of the battery cell.The voltage monitoring system VMS therefore constantly monitors theoutput voltage of each battery cell during vehicle driving. The cellmonitoring unit CMU judges whether or not the output voltage of eachbattery cell is within the charging upper limit voltage at the start ofthe regenerative braking operation. If there is a battery cell whoseoutput voltage is larger than the charging upper limit voltage then thecell monitoring unit CMU issues an overcharge warning to the batterymanagement unit BMU. The battery management unit BMU opens the relaysREL1 and REL2 according to the overcharge warning, and stops thecharging of the battery pack assembly.

The cell monitoring unit CMU moreover continues to monitor the outputvoltage of the battery cells even during charging from the regenerativebraking operation. When a battery cell is discovered where the outputvoltage has reached the charging upper limit voltage, the cellmonitoring unit CMU sends the overcharging warning to the batterymanagement unit BMU. The battery management unit BMU opens the relaysREL1 and REL2 according to the overcharging warning to stop the chargingof the battery pack assembly. Overcharging of the battery pack assemblyis prevented in this way.

The description of the voltage monitoring system VMS operation assumesthat the voltage of the battery cell can be correctly detected asalready described. In fact however, the battery cell output voltagecannot always be detected correctly. For example if the line between thevoltage monitoring modules VMM1 through VMMn and the battery packassembly is disconnected (broken wire) then there will be an abnormalvoltage drop or voltage rise at the line disconnect point, and the cellmonitoring unit CMU will not be able to calculate the voltage correctly.If this type of wire disconnection occurs then the monitoring of batterycell output voltages which is the purpose of the voltage monitoringsystem VMS is impossible so that detection of wire disconnectionbreakdowns (electrical opens) is required.

A correct range of output voltage values is therefore pre-stored in thecell monitoring unit CMU. If the calculated output voltage value of thebattery cells deviate from the correct range, then the cell monitoringunit CMU judges that a wire disconnect breakdown has occurred. The cellmonitoring unit CMU notifies the battery management unit BMU that a wiredisconnect breakdown has occurred. The battery management unit BMU opensthe relays REL1 and REL2 according to the wire disconnect breakdownnotification and cuts off the coupling between the inverter INV and thebattery pack assembly. The system in this way prevents further problemsfrom occurring. The battery management unit BMU also notifies the enginecontrol unit ECU that a wire disconnect breakdown has occurred. Theengine control unit ECU displays the wire disconnect breakdowninformation for example on a display device mounted at the driver's seatto inform the driver that a breakdown has occurred. The voltagemonitoring system VMS is in this way capable of detecting that a wiredisconnect breakdown has occurred.

The structure and the operation of the voltage monitoring system VMS arenothing more than examples. Therefore the cell monitoring unit CMU andthe battery management unit BMU can for example be unified into onecircuit block. Moreover, all or a portion of the functions delegated tothe cell monitoring unit CMU and the battery management unit BMU can bemutually handled by either of these units. Furthermore, the cellmonitoring unit CMU, the battery management unit BMU, and the enginecontrol unit ECU can be unified into one circuit block. The enginecontrol unit ECU can serve as a substitute to handle all or a portion ofthe functions of the cell monitoring unit CMU and the battery managementunit BMU.

The voltage monitoring system of the first embodiment is a voltagemonitoring system for monitoring multiple battery cells mutually coupledin series, and which includes the voltage monitoring modules VMM1through VMMn for operating from a voltage received from at least onebattery cell among multiple battery cells and monitoring the batterycell; and a module control circuit (e.g. cell monitoring unit CMU) forcontrolling the voltage monitoring modules VMM1 through VMMn. Thevoltage monitoring system of the first embodiment includes one featurein the configuration of the power supply circuit for the voltagemonitoring modules VMM1 through VMMn and the operation of the modulecontrol circuits (e.g. cell monitoring unit CMU). The voltage monitoringmodules VMM1 through VMMn configuration is therefore first of alldescribed utilizing the voltage monitoring module VMM1 as an example. Inthe following description, the same reference numerals are attached tothe same sections as described above and that description omitted.

FIG. 4 is a block diagram of the voltage monitoring module VMM1 of thefirst embodiment. The voltage monitoring module VMM1 as shown in FIG. 4includes internal circuits (circuits including the cell balance circuitsCB1-CBm, voltage measurement circuit VMC) serving as load circuits, aregister VMC_REG, a control circuit VMC_CON, and a communication circuitVMC_C. Also, the power supply circuit VMM_S generates a load currentIload and an internal voltage Vout from the power supply voltage appliedfrom the power supply terminal VCC, and supplies this load current Iloadand an internal voltage Vout to the load circuits.

As operating modes, the voltage monitoring module VMM1 of the firstembodiment includes an initializing mode, a normal operating mode, and asleep mode. The initializing mode is an operating mode that sets theoperating current of the voltage monitoring module VMM in normaloperating mode. The normal operating mode is a mode for the voltagemonitoring module VMM to make voltage measurements of the battery cellsEC1-ECm. The sleep mode is a power saving mode in which the voltagemonitoring module VMM stops the voltage measurements of the batterycells EC1-ECm. Even though the operation of the main function circuitssuch as the voltage measurement circuit for the AD converter VMC_ADC wasstopped by this sleep mode, those circuits required for communicationwith outside sections such as the communication circuit VMM_C, theregister VMC_REG, and the control circuit VMC_CON as well as circuitsrequired for shifting operation to the following operating modes stilloperate. Moreover, the power supply circuit VMM_S continues outputtingthe internal voltage Vout and the output current Iout even in the sleepmode.

In normal operating mode, the power supply circuit VMM_S generates afirst reference current according to the first current code suppliedfrom an outside unit, and along with generating an output currentaccording to the first reference current, draws the adjusting currentIadj from the output current (except for the load current Iload) at theground terminal VSS. In sleep mode, the power supply circuit VMM_Sgenerates a second reference current smaller than the first referencecurrent according to a second current code supplied from an outsideunit, and along with generating an output current according to thesecond reference current, draws the adjusting current Iadj from theoutput current (except for the load current Iload) at the groundterminal VSS. The power supply circuit VMM_S can in this way maintain afixed operating current during either of the normal operating mode orsleep mode, regardless of the size of the load current Iload.

The power supply circuit VMM_S includes the current detector resistorRid, the operating current measurement circuit 10, the regulator circuit11, and the adjusting current control circuit 12. In the voltagemonitoring module VMM1 of the first embodiment, the power supply circuitVMM_S differs from a typical power supply circuit in the point ofincluding a current detector resistor Rid, the operating currentmeasurement circuit 10, and the adjusting current control circuit 12.

The current detector resistor Rid is mounted between the power supplyterminal VCC, regulator 11, and the adjusting current control circuit12. Operating current from the power supply terminal VCC flowing in theregulator 11, and the adjusting current control circuit 12, flowsthrough the current detector resistor Rid. A voltage differential Vd isgenerated across both ends of the current detector resistor Ridaccording to the size of the operating current.

The operating current measurement circuit 10 measures the operatingcurrent according to the operating current measuring command sent fromthe cell monitoring unit CMU subsequent to the operating currentswitching command. More specifically, the operating current measurementcircuit 10 measures the size of the operating current flowing in thepower supply circuit VMM_S based on the voltage differential Vd, andgenerates the operating current measurement value Imon. In the operatingcurrent measurement circuit 10 of the first embodiment, the operatingcurrent measurement value Imon is set to a value that corresponds to theload current Iload, in order for the adjusting current control circuit12 to operate in initializing mode where generation of the adjustingcurrent Iadj was stopped according to the operation current switchingcommand. The operation current measurement circuit 10 stores theoperation current measurement value in the register VMC_REG. Further, inthe first embodiment, the operating current measurement circuit 10starts measuring the operating current according to the measurementstart signal (not shown in drawing) generated in response to themeasuring command that the control circuit VMC_CON received by way ofthe communication circuit VMM_C from the cell monitoring unit CMU.

The regulator circuit 11 generates an internal voltage Vout and outputcurrent from the power supply voltage supplied from the power supplyterminal VCC, and supplies the internal voltage Vout to the loadcircuit. The regulator circuit 11 increases or decreases the outputcurrent according to the switched reference current generated by theadjusting current control circuit 12.

Along with generating an adjusting current Iadj so that the operatingcurrent consumed by the voltage monitoring module according to firstoperating current setting command sent from the cell monitoring unit CMUreaches a specified value corresponding to the first operating currentsetting command; the adjusting current control circuit 12 also stopsgenerating the adjusting current Iadj according to the operating currentswitching command sent from the cell monitoring unit CMU. Moreover, thecell monitoring unit CMU sends a second operating current settingcommand based on the operating current measured by the operating currentmeasurement circuit 10, and the adjusting current control circuit 12 inaccordance with the second operating current setting command, generatesthe adjusting current Iadj in order to reach a specified valuecorresponding to the second operating current setting command. Theadjusting current control circuit 12 generates the adjusting currentIadj so that the sum of this adjusting current and the load currentconsumed by circuits other than the adjusting current control circuit 12within the voltage monitoring module VMM1 attains a specified valuecorresponding to the first or the second operating current settingcommand. Further, adjusting current control circuit 12 generates areference current to serve as a reference for the size of the outputcurrent of the regulator circuit 11.

The regulator circuit 11 and the adjusting current control circuit 12 ofthe first embodiment are described next in detail. FIG. 5 is a blockdiagram of the regulator circuit 11 and the adjusting current controlcircuit 12 of the first embodiment.

The regulator circuit 11 as shown in FIG. 5 includes a fixed voltagegenerator unit 21, a first differential amplifier amp0, an outputtransistor P0, a first resistor R1, and a second resistor R2.

The fixed voltage generator unit 21 generates a reference voltage VBGR.This fixed voltage generator unit 21 is for example a bandgap voltagesupply that outputs a bandgap voltage as the reference voltage VBGR.This reference voltage VBGR in other words has an extremely smallfluctuation width relative to the temperature.

The output transistor P0 utilizes for example a PMOS transistor. Thesource of the output transistor P0 is coupled to the power supplyterminal VCC. The first resistor R1 and the second resistor R2 arecoupled in series between the drain and the ground terminal VSS of thePMOS transistor P0. The coupling point between the first resistor R1 andthe drain of the PMOS transistor P0 is the output terminal of theregulator circuit 11. The fixed voltage generator unit 21 inputs areference voltage VBGR to the inverting input terminal on the firstdifferential amplifier amp0, and the non-inverting input terminal iscoupled to the coupling point between the first resistor R1 and thesecond resistor R2. The output signal from the differential amplifieramp0 is supplied to the gate of the PMOS transistor P0. The firstdifferential amplifier amp0 operates based on the ground voltage and thepower supply voltage supplied from the power supply terminal VCC. Theregulator circuit 11 in other words configures a forward amplifiercircuit comprised of a first differential amplifier amp0, an outputtransistor P0, a first resistor R1, and a second resistor R2. Thisforward amplifier circuit sets the amplification rate according to theresistance ratio of the resistance value for the first resistor R1 andthe resistance value for the second resistance R2. The forward amplifiercircuit for the regulator circuit 11 amplifies the reference voltageVBGR according to the amplification rate and outputs an internal voltageVout.

The adjusting current control circuit 12 includes a current settingcircuit 22 and a current consumption circuit 23. The current settingcircuit 22 generates a reference current serving as the reference forthe side of the output current of the regulator circuit 11. The currentconsumption circuit 23 consumes the adjusting current Iadj for the loadcurrent Iload of the load circuit and the output current of theregulator circuit 11.

The current setting circuit 22 includes a current setting resistor Ris,and a PMOS transistor P1. The current setting resistor Ris varies theresistance value according to the current code adj. The PMOS transistorP1 configures the output transistor P0 and the current mirror. Thesource of the PMOS transistor P1 is coupled to the power supply terminalVCC, the drain is coupled to one end of the current setting resistorRis, and the gate is coupled to the gate of the output transistor P0.One terminal of the current setting resistor Ris is coupled to theground terminal VSS. The other terminal of the current setting resistorRis is coupled to the non-inverting input terminal of the seconddifferential amplifier amp1 of the current consumption circuit 23. Here,the inverting input terminal of the second differential amplifier amp1is coupled to the non-inverting input terminal of the first differentialamplifier amp0. Consequently, this virtual electrical short between thefirst differential amplifier amp0 and the second differential amplifieramp1 generates a voltage approximately equivalent to the referencevoltage VBGR in the non-inverting input terminal of the seconddifferential amplifier amp 1. Also a voltage differential approximatelyequivalent to the reference voltage VBGR on both ends of the currentsetting resistor Ris so that a reference current Iref as the value ofthe reference voltage VBGR divided by the resistance value of thecurrent setting resistor Ris then flows in the current setting resistorRis.

In the voltage monitoring modules VMM1 of the first embodiment, theratio of the gate width W of the output transistor P0, and the PMOStransistor P1 (in other words the transistor size ratio) i:j is set toi>j. Therefore a larger current flows is set in the output transistor Pothan in the reference current Iref. So in the case of a ratio ofi:j=5:1, the output current flowing in the output transistor P0 will befive times larger than the reference current Iref. In the regulatorcircuit 11, the current Ip0 b which is the output current Iout flowingin the output transistor P0 minus the current Ip0 a flowing in theresistors R1, R2, is output from the output terminal. The current Ip0 ais considerably smaller compared to the current Ip0 b so that in thefollowing description Ip0 b is considered equal to Iout.

The current consumption circuit 23 includes the second differentialamplifier amp1, the PMOS transistor P2, and the NMOS transistor Ndi. Thenon-inverting input terminal of the second differential amplifier amp 1is coupled to one end of the current setting resistor Ris, and theinverting terminal is coupled to the non-inverting input terminal of thefirst differential amplifier. The second differential amplifier amp 1operates based on the ground voltage and the internal voltage Vout thatis output from the regulator circuit 11. The source of the PMOStransistor P2 is coupled to the output terminal of the regulator circuit11, the drain is coupled to the drain of the NMOS transistor Ndi, andthe gate is coupled to the output terminal of the second differentialamplifier amp1. The source of the NMOS transistor Ndi is coupled to theground terminal VSS, and the gate is coupled to the drain. The NMOStransistor Ndi in other words operates as a diode. This diode functionsas a load circuit for the current consumption circuit 23. The PMOStransistor P2 extracts the current Icmp from the output current Ioutaccording to the output signal from the second differential amplifieramp1, and supplies it to the NMOS transistor Ndi. A standby controlsignal STB is applied to the second differential amplifier amp1. Whenthe standby control signal STB is in the enable state, the seconddifferential amplifier amp1 stops the operation, and stops the currentconsumption circuit 23 operation. The reference current Iref still flowseven if the current consumption circuit 23 operation was stopped by thestandby control signal STB. However, the reference current Iref isextremely small compared to the operating current in the voltagemonitoring modules VMM1 and so is a level that can mostly be ignored interms of effects on the size of the operating current.

The structure of the current setting resistor Ris is described next.FIG. 6 is a block diagram showing the current setting resistor Ris. Thecurrent setting resistor Ris as shown in FIG. 6 includes multipleresistors Ri1-Rik coupled in parallel, and the switches SWi1-SWikcoupled in series to the respective plural resistors, and a decoder. Acurrent code adj is input to the decoder. This current code adj is avalue supplied by the operating current setting command. The decodersets any one of the switches SWi1-SWik to a conducting state accordingto the value of the current code adj. The resistors Ri1-Rik each possessdifferent resistance values. One among the resistors Ri1-Rik is set as aresistor enabled during sleep mode, and has a considerably higherresistance value than the other resistors. The current setting resistorRis includes a terminal TMU serving as one end of the current settingresistor Ris and a terminal TML serving as the other end (of the currentsetting resistor Ris).

The operation of the regulator circuit 11 and the adjusting currentcontrol circuit 12 of the first embodiment are described next. FIG. 7 isa timing chart showing the operation of the regulator circuit 11 and theadjusting current control circuit 12 of the first embodiment. In theexample shown in FIG. 7, the load circuit Iload increases and decreasesalong with the passage of time.

As shown in FIG. 7, the current consumption circuit 23 lowers thecurrent Icmp when the load current Iload has increased. The current Ioutincreases when the load current I load has increased. There is nofluctuation in the current Ip0 a at this time. The reference currentIref also increases according to the increases in this current Iout. Thevoltage differential across both ends of the current setting resistorRis therefore also increases. In other words, the voltage in thenon-inverting input terminal of the second differential amplifier amp1rises. The second differential amplifier amp1 therefore raises the(output) voltage Vn1 of the output signal applied to the gate of thePMOS transistor P2, and lowers the current drive capability of the PMOStransistor P2. The current Icmp therefore decreases when the loadcurrent Iload has increased. The current Iout decreases according to thedrop in the current Icmp and the current Icmp attains a stable state.

However, if the load current Iload has decreased, then the currentconsumption circuit 23 raises the current Icmp. The current Ioutdecreases when the load current Iload has decreased. There is nofluctuation in the current Ip0 a at this time. The reference currentIref then lowers according to the drop in this current Iout. The voltagedifferential across both ends of the current setting resistor Ristherefore lowers. In other words, the voltage of the non-inverting inputterminal of the second differential amplifier amp1 then drops. Thesecond differential amplifier amp1 therefore causes a voltage drop inthe voltage Vn1 of the output signal applied to the gate of the PMOStransistor P2, and raises the current drive capability of the PMOStransistor P2. The current Icmp therefore increases if the load currentIload has decreased. The current Iout then increases according to theincrease in the current Icmp, and the current Icmp attains a stablestate.

The regulator circuit 11 and the adjusting current control circuit 12 ofthe first embodiment therefore function in this way so that theadjusting current control circuit 12 increases or decreases the currentIcmp in order to cancel out the increase and decrease in the loadcurrent. The power supply circuit of the first embodiment can thereforehandle an increase or decrease in the load current Iload whilemaintaining a fixed output current Iout in the regulator circuit 11.

The operation of regulator circuit 11 and the adjusting current controlcircuit 12 of the first embodiment is here described utilizing numericalformulas. First of all, the total current I_total of current flowinginto the regulator circuit 11 and the adjusting current control circuit12 from the power supply terminal VCC can be expressed by way of formula(1). In this formula (1), the Iout is set equal to Ip0 b. In thisformula ofI_total=Iout+Iref+Iamp0  (1),and the Iout in formula (1) is the size of the regulator circuit 11output current; Iref is the size of the reference current generated bythe current setting circuit 22; and Iamp0 is the size of the operatingcurrent of the first differential amplifier amp0.

The output current Iout of the regulator circuit 11 is expressed next informula (2). In this formula (2),I_out=Ip0a+Iload+Icmp+Iamp1  (2),and the Ip0 a in formula (2) is the size of the current flowing in thefirst resistor R1 and the second resistor R2; the Iload is the size ofthe load current supplied to the load circuit; Icmp is the current drawnby the PMOS transistor P2 of the current consumption circuit 23; andIamp1 is the size of the operating current of the second differentialamplifier amp1.

Here, in the power supply circuit VMM_S, when the relation of the outputtransistor P0 and the PMOS transistor P1 is a transistor size ratio ofN:1, then the relation in formula (3) is obtained between the referencecurrent Iref and the output current Iout of the regulator circuit 11.Iout=N×Iref  (3)

When Ris is set as the size of the current setting resistor then thesize of the reference current Iref is determined by the relationexpression in formula (4).Iref=VBGR/Ris  (4)

From the formulas (1), (3), (4), the current value I_total is thenexpressed by the formula (5).I_total=N×Iref+Iref+Iamp0=(1+N)Iref+Iamp0=(1+N)×VGBR/Ris+Iamp0  (5)In this formula (5), the Iamp0 is the consumption current of the firstdifferential amplifier amp0 so that the value is fixed regardless of theoperation state of the load circuit. The reference voltage VBGR is alsofixed regardless of the state of the load circuit. Moreover, the currentsetting resistor Ris is a fixed value unless the input current code isrewritten. In other words, formula (5) reveals that the current flowingin the regulator circuit 11 and the adjusting current control circuit 12is maintained at approximately a fixed value. Also in the power supplycircuit VMM_S of the first embodiment, one can perceive from the formula(5) that the size of I_total can be set to a small value by setting thesize of the resistance value of the current setting resistor Ris to alarge value. One can also understand that the formula (5) does notinclude elements such as an offset component for the differentialamplifier so that the small current value I_total can be accurately setin the power supply circuit VMM_S according to the first embodiment. Onecan also understand from formula (3) that the output current Iout ofregulator circuit 11 can be maintained at approximately a fixed value.

Among the elements in formula (2), the current Ip0A is a constantdetermined by the internal voltage Vout, the first resistor R1 and thesecond resistor R2, and that the Iamp1 is approximately a fixed valuenot dependent on the state of the load circuit which is the operatingcurrent of the second differential amplifier. One can thereforeunderstand that the output current Iout is a fixed value, and fromformula (2) that a fixed Iload+Icmp are maintained. In other words, whatcan also be understood is that the load current Iload increases ordecreases according to the state of the load circuit and that thecurrent Icmp varies to cancel out the increase or decrease in the loadcurrent Iload.

The consumption current Iamp0 of the first differential amp0 isextremely small compared to the output current Iout and the referencecurrent Iref so in the following description Iout+Iref are utilized asthe power supply circuit operating current. Moreover, the current Ip0 ais extremely small compared to the total value of the load currentIload, the consumption current Iamp1 of the first differential amplifieramp1, and the drawn current Icmp so that in the following description,the Iload+Icmp+Iamp1 are utilized as the output current Iout. Also, theadjusting current Iadj that the adjusting current control circuit 12bleeds out to the ground terminal VSS contains the current Icmp and thecurrent Iamp1.

The power supply circuit VMM_S of the first embodiment according to theabove description, the current setting circuit 22 generates a referencecurrent Iref based on the reference voltage VBGR and the resistancevalue of the current setting resistor Ris. The current setting circuit22 sets the output current Iout of the regulator circuit 11 based on theapplicable reference current Iref. Moreover, in the power supply circuitVMM_S, the current consumption circuit 23 draws the adjusting currentIadg for the output current Iout and load current Iload to the groundterminal. The power supply circuit VMM_S can in this way set theoperating current I_total to a fixed value regardless of the increase ordecrease in the load current Iload.

In the power supply circuit VMM_S, the reference current Iref can beaccurately set in a wide dynamic range by utilizing the current code adjto vary the resistance value of the current setting resistor Ris. Thepower supply circuit VMM_S in this way can maintain the operatingcurrent I_total at a fixed value in either case of a large operatingcurrent I_total and a small operating current I_total.

The methods for setting the operating current of the voltage monitoringmodules VMM1 through VMMn are described next. In the voltage monitoringsystem of the first embodiment, the cell monitoring unit CMU sets therange of the operating current for the voltage monitoring modules VMM1through VMMn. The voltage monitoring modules VMM1 through VMMn then setthe operating current based on the current code that was set by the cellmonitoring unit CMU.

In the first embodiment, the cell monitoring unit CMU sends theoperating current setting command, the operating current switchingcommand, and the operating current measuring command to the voltagemonitoring modules VMM1 through VMMn. The operating current settingcommand includes the current code adj. If the voltage monitoring modulesVMM1 through VMMn have received the operating current setting command,then the adjusting current control circuit 12 generates an adjustingcurrent Iadj so that the operating current consumed by the voltagemonitoring modules VMM1 through VMMn attains a specified valuecorresponding to the operating current setting command. Also, if thevoltage monitor modules VMM1 through VMMn have received the operatingcurrent switching command, then the adjusting current control circuit 12stops generating the adjusting current Iadj. If the voltage monitoringmodules VMM1 through VMMn have received the operating current measuringcommand, then the operating current is measured. The operating currentmeasuring command is sent subsequent to the operating current switchingcommand. Moreover, after rewriting the value of the current code adjcontained in the operating current setting command based on the measuredoperating current, the cell monitoring unit CMU sends an operatingcurrent setting command including the rewritten current code adj. Theoperating current setting command containing the not yet rewrittencurrent code adj is equivalent to the first operating current settingcommand, and the operating current setting command containing therewritten current code adj is equivalent to the second operating currentsetting command.

Also in the first embodiment, the cell monitoring unit CMU outputs afirst current code (e.g. operating current code) specifying the size ofthe first operating current in normal operating mode for monitoring thebattery cells by the load circuit; which is current value that is thesame or larger than the load current Iload of the voltage monitoringmodules VMM1 through VMMn. The first operating current setting commandand the second operating current setting command include the firstcurrent code. The cell monitoring unit CMU outputs a second current code(e.g. sleep current code) specifying the size of a second operatingcurrent smaller than the first current code, and which is the size ofthe operating current in sleep mode for stopping the monitoring of thebattery cells by the load circuit. The operating current specified bythe second current code is measured at times such as prior to productshipping or is specified as an operating current larger than theoperating current that was calculated for sleep mode in the designstage. The operating current setting command containing this secondcurrent code is equivalent to the third operating current settingcommand. Along with performing operation based on the first operatingcurrent specified by the first current code during normal operatingmode, the power supply circuit VMM_S for the voltage monitoring modulesVMM1 through VMMn, also maintains the first operating current at a fixedvalue regardless of the increase or decrease in the load current Iload.Along with performing operation based on the second operating currentset by the second current code for sleep mode, the power supply circuitVMM_S for the voltage monitoring modules VMM1 through VMMn, alsomaintains the second operating current at a fixed value regardless ofthe increase or decrease in the load current Iload.

The cell monitoring unit CMU executes commands such as the sleep modeshift command, the normal operating mode shift command, the operatingcurrent measurement value readout command, and the battery cell voltagemeasurement value readout command on the voltage monitoring modules VMM1through VMMn.

FIG. 8 is a block diagram of the cell monitoring unit CMU. The cellmonitoring unit CMU as shown in FIG. 8 includes a processor element 30,a memory 34, a communication unit 35, and a timer 36. The memory 34stores a program to operate the voltage monitoring modules, and a secondcurrent code (sleep current code) utilized during sleep mode. Thecommunication unit 35 is a communication interface for performingcommunication between the cell monitor unit CMU and voltage monitoringmodules or the battery management unit BMU. The timer 36 measures thespecified time set based on the program.

The processor element 30 loads the program from the memory 34 andoperates based on the applicable program. In the example shown in FIG.8, the processor element 30 includes an arithmetic processing unit 31, astate control unit 32, and a current setting register 33. The arithmeticprocessing unit 31 includes a memory interface and communicates by wayof the applicable memory interface with the memory 34. The arithmeticprocessing unit 31 generates a first current code (operating currentcode) based on the program loaded from the memory 34 and makes apass/fail decision of the battery cell voltage measurement results. Thestate control unit 32 outputs a control command to the voltagemonitoring modules VMM1 through VMMn based on the interrupt commandsapplied from the other devices by way of the communication unit 35 andinterrupt commands that the arithmetic processing unit 31 supplied byway of the bus. These control commands include the operating currentsetting command, the operating current switching command, the operatingcurrent measuring command, the sleep mode shift command, the normaloperating mode command, the operating current measurement value loadcommand, and the battery cell voltage measurement value load command.The current measurement register 33 stores the operating currentmeasurement values loaded from the voltage monitoring modules VMM1through VMMn.

The procedure used by the cell monitoring unit CMU for setting the sizeof the operating current consumed by the voltage monitoring modules VMM1through VMMn in normal operating mode is described next. FIG. 9 is asequence diagram showing the procedure for setting the operating currentduring normal operating mode in the voltage monitoring system of thefirst embodiment.

As shown in FIG. 9, the voltage monitoring modules VMM1 through VMMn andthe cell monitoring unit CMU start operation from the startup process.This startup process for example begins from a power-on reset signalgenerated according to the voltage level of the power supply voltage.When the startup procedure ends, the voltage monitoring modules VMM1through VMMn first of all start operating in the initializing mode. Thisinitializing mode is a mode that stops the current consumption circuit23 of the adjusting current control circuit 12 based on the standbycontrol signal STB output by the control circuit VMC_CON within thevoltage monitoring modules VMM1-VMMn. Namely, in initializing mode theoperating current in the power supply circuit VMM_S fluctuates accordingto the load current Iload without drawing any adjusting current Iadj byway of the current consumption circuit 23. The voltage monitoringmodules VMM1-VMMn shift to initializing mode may be made based on acommand from the cell monitoring unit CMU after the startup processingended. When the startup process is complete, the cell monitoring unitCMU outputs an operating current measuring command to the voltagemonitoring modules VMM1-VMMn.

The voltage monitoring modules VMM1-VMMn measure the size of the currentflowing in the power supply circuit VMM_S according to receiving of theoperating current measuring command output by the cell monitoring unitCMU and generate operating current measurement values according to thesize of the load current. The voltage monitoring modules VMM1-VMMn storethe operating current measurement values in the register VMC_REG.

The cell monitoring unit CMU outputs an operating current measurementvalue load command to the voltage monitoring modules VMM1-VMMn. Thevoltage monitoring modules VMM1-VMMn send operating current measurementvalues stored in the register VMC_REG to the cell monitoring unit CMUbased on the applicable load commands.

The cell monitoring unit CMU stores the received operating currentmeasurement values in the current measurement register 33. Thearithmetic processing unit 31 of the processor element 30 specifies theoperating current measurement value that is the largest value among theoperating current measurement values stored in the current measurementregister 33. The arithmetic processing unit 31 further generates a firstcurrent code (e.g. operating current code) corresponding to thespecified maximum operating current measurement value. This operatingcurrent code includes a value specifying a current value that is thesame or greater than the maximum operating current measurement value.This operating current code is preferably set to a current value towhich a specified margin has been added to the maximum operating currentmeasurement value. This added margin is for the purpose of achievingstable circuit operation relative to fluctuations in the load current.

The cell monitoring unit CMU next sends an operating current settingcommand including the generated operating current code to the voltagemonitoring modules VMM1-VMMn. This operating current code is stored inthe register VMC_REG of the voltage monitoring modules VMM1-VMMn. Then,along with the adjusting current control circuit 21 switching theoperating current code stored in the register VMC_REG to the referencecurrent value as the current code adj, the control circuit VMC_CON setthe standby control signal STB to the enable state. The voltagemonitoring modules VMM1-VMMn in this way start operation in the normaloperating mode.

In normal operating mode, the power supply circuit VMM_S operates fromoperating current based on a first current set by the normal currentcode. In other words, in the normal operating mode, any of the voltagemonitoring modules can set the operating current based on the operatingcurrent code generated by the central monitoring unit CMU even in thecase of multiple voltage monitoring modules and can equalize theoperating current among the voltage monitoring modules.

The voltage monitoring modules VMM1-VMMn then start measuring thebattery cell voltages. The voltage monitoring modules VMM1-VMMn thensend the battery cell voltage measurement results to the centralmonitoring unit CMU in response to a request from the central monitoringunit CMU. This battery cell voltage measurement processing is performedat specified intervals.

In the voltage monitoring system of the first embodiment, the process torewrite (update) the operating current is also performed at specifiedintervals. The procedure for the central monitoring unit CMU to rewritethe size of the voltage monitoring modules VMM1-VMMn operating currentis therefore described next. FIG. 10 is a sequence diagram showing theprocedure for rewriting the operating current during normal operatingmode in the voltage monitoring system of the first embodiment. In thesequence diagram shown in FIG. 10, the detailed operation in therespective circuit blocks was simplified in order to focus on thesending and receiving of commands with the voltage monitoring modulesVMM1-VMMn and the cell monitoring unit CMU, however the detailedoperation of the circuit blocks for each command is the same operationas shown in FIG. 9.

As shown in FIG. 10, when a specified time on a timer in the cellmonitoring unit CMU elapses, then the cell monitoring unit CMU sends anoperating current switching command to the voltage monitoring modulesVMM1-VMMn. The voltage monitoring modules VMM1-VMMn shift to theinitializing mode in response to the operating current switchingcommand. The adjusting current control circuit 12 in this way stops thecurrent consumption circuit 23 based on the standby control signal STBoutput by the control circuit VMC_CON within the voltage monitoringmodules VMM1-VMMn.

The cell monitoring unit CMU sends an operating current measuringcommand to the voltage monitoring modules VMM1-VMMn subsequent to theoperating current switching command. The voltage monitoring modulesVMM1-VMMn measure the size of the voltage measurement module operatingcurrent according to the operating current measuring command, andgenerate an operating current measurement value corresponding to thesize of the load current. The voltage monitoring modules VMM1-VMMn thenstore the operating current measurement values in the register VMC_REG.

The cell monitoring unit CMU next outputs an operating currentmeasurement value load command to the voltage monitoring modulesVMM1-VMMn. The voltage monitoring modules VMM1-VMMn send the operatingcurrent measurement values stored in the register VMC_REG to the cellmonitoring unit CMU based on the applicable load command.

The cell monitoring unit CMU then specifies an operating currentmeasurement value that is the maximum value among the received operatingcurrent measurement values, and rewrites the operating current code to avalue corresponding to the specified maximum operating currentmeasurement value. The cell monitoring unit CMU next sends an operatingcurrent setting command including the rewritten operating current codeto the voltage monitoring modules VMM1-VMMn. The voltage monitoringmodules VMM1-VMMn then generate an adjusting current Iadj correspondingto the operating current code contained in the received operatingcurrent setting command and start the operation.

After a specified time on the timer then elapses in the cell monitoringunit CMU, the cell monitoring unit CMU sends the operating currentswitching command to the voltage monitoring modules VMM1-VMMn, andrewrites the operating current cod based on the maximum operatingcurrent of the voltage monitoring modules VMM1-VMMn at that time, andrewrites the size of the voltage monitoring modules VMM1-VMMn operatingcurrent by utilizing the rewritten operating current code.

The operating current I_total for the voltage monitoring module that wasset according to the processing in FIG. 9 and FIG. 10 is described. FIG.11 shows a table for describing the operating current during normaloperating mode in the voltage monitoring module in the voltagemonitoring system of the first embodiment. In the example shown in FIG.11, the maximum operating current among the voltage monitoring modulesin initializing mode is 45 mA in the voltage monitoring module VMM1. Avalue that is larger than 4.5 mA (e.g. 5 mA) is therefore specified bythe normal current code in the voltage monitoring system of the firstembodiment. The operating current of all voltage monitoring modules innormal operating mode in this way becomes 5 mA in the voltage monitoringsystem of the first embodiment.

Next, FIG. 12 shows a sequence diagram of the procedure for shifting thevoltage monitoring modules in the voltage monitoring system of the firstembodiment from normal operating mode to sleep mode. As shown in FIG.12, when for example the battery management unit BMU inputs a sleepinstruction to the state control unit 32 of the cell monitoring unitCMU, then the state control unit 32 sends a sleep mode shift command tothe voltage monitoring module. The control circuit VMC_CON in this waysets the circuits such as the voltage measurement circuit to a stopstate in the voltage monitoring modules VMM1-VMMn.

The cell monitoring unit CMU next sends an operating current settingcommand including a sleep current code to the voltage monitoring modulesVMM1-VMMn. The voltage monitoring modules VMM1-VMMn then stores thesleep current code in the register VMC_REG. The voltage monitoringmodules VMM1-VMMn then starts operation by way of the second operatingcurrent that was set by the sleep current code. This sleep current codeis for specifying a preset operating current and the sleep current codevalue is determined by simulation in the design stage or an inspectionperformed after manufacture.

The I_total for the voltage monitoring module set by the operatingcurrent according to the process in FIG. 12 is described. FIG. 13 showsa table describing the operating current during sleep mode in thevoltage monitoring modules of the voltage monitoring system of the firstembodiment. In the example shown in FIG. 13, the operating current ofthe voltage monitoring modules in sleep mode are set to 30 μA in all thevoltage monitoring modules. In this sleep mode, the load current of theload circuit is 25 μA in all of the voltage monitoring modules, and theadjusting current Iadj flowing from the adjusting current controlcircuit 12 is 5 μA in all of the voltage monitoring modules. However,when there are large irregularities (variations) in the load current ofthe load circuit due to manufacturing variations, then the error in theload current due to these irregularities is absorbed by the adjustingcurrent Iadj of the adjusting current control circuit 12.

Next, FIG. 14 shows a sequence diagram of the procedure for shiftingfrom sleep mode to the normal operating mode in the voltage monitoringmodule of the voltage monitoring system of the first embodiment. Asshown in FIG. 14, for example, the battery management unit BMU, etc.input a normal operating mode instruction to the state control unit 32of the cell monitoring unit CMU, then the state control unit 32 sends anormal operating mode shift command to the voltage monitoring module.The control circuit VMC_CON in this way sets the voltage measurementcircuit, etc. to the operating state in the voltage monitoring modulesVMM1-VMMn, and moreover shifts the adjusting current control circuit 12to initializing mode as the stop state.

Then in initializing mode, the cell monitoring unit CMU and the voltagemonitoring modules VMM1-VMMn perform the same processing as theprocedure for setting the normal current code during startup such as forobtaining the operating current measurement values.

In the voltage monitoring system of the first embodiment describedabove, an adjusting current Iadj is generated in each of the voltagemonitoring modules VMM1-VMMn in order to equalize the operating currentin the voltage monitoring modules VMM1-VMMn. The voltage monitoringmodules VMM1-VMMn at this time set the operating current includingadjusting current Iadj to a specified value that corresponds to theoperating current code adj contained in the first operating currentsetting command sent from the cell monitoring unit CMU. In the voltagemonitoring system of the first embodiment, the voltage monitoringmodules VMM1-VMMn stop the adjusting current Iadj according to theoperating current switching command sent by the cell monitoring unitCMU, and the voltage monitoring modules VMM1-VMMn measure the operatingcurrent with the adjusting current Iadj in a stop state (initializingmode) according to the operating current measuring command sentfollowing the operating current switching command sent by the cellmonitoring unit CMU, and the cell monitoring unit CMU rewrites theoperating current code based on this measured operating current and alsosends an operating current setting command (second operating currentsetting command) including the rewritten operating current code, and thevoltage monitoring modules VMM1-VMMn generate an adjusting current Iadjso that the operating current attains a specified value corresponding tothe second operating setting command. In other words, in the voltagemonitoring system of the first embodiment, the size of the operatingcurrent including the adjusting current Iadj consumed by the voltagemonitoring modules VMM1-VMMn can be rewritten (or updated) according tothe size of the load current Iload except for the adjusting currentIadj. The voltage monitoring system of the first embodiment can in thisway maintain the operating current among the voltage monitoring modulesin a uniform (equalized) state by rewriting the operating current codeso as to increase the size of the operating current including theadjusting current Iadj, even in cases where the load current Iload wasincreased in the voltage monitoring modules VMM1-VMMn. Moreover, thevoltage monitoring system of the first embodiment can maintain theoperating current among the voltage monitoring modules in a uniform(equalized) state by rewriting the operating current code so as todecrease the size of the operating current including the adjustingcurrent Iadj, even in cases where the load current Iload has increasedin the voltage monitoring modules VMM1-VMMn. Also in the voltagemonitoring system of the first embodiment, the operating current can beequalized to the most ideal value by resetting, even in cases where thesize of the operating current must be reset, so that an imbalance in theconsumption current among the voltage monitoring modules can be limitedand the battery life can be extended.

In the voltage monitoring system of the first embodiment, the cellmonitoring unit CMU sets the operating current in the voltage monitoringmodules based on the normal current code specifying an operating currentlarger than the maximum value of the load current in the voltagemonitoring modules. The voltage monitoring system of the firstembodiment can in this way equalize the operating current in the voltagemonitoring modules.

The vehicular power supply device in Japanese Unexamined PatentApplication Publication No. 2010-81692 does not contain a mechanism forequalizing the current consumption in low current consumption modes suchas sleep mode. As shown in FIG. 18, the vehicular power supply devicedescribed in Japanese Unexamined Patent Application Publication No.2010-81692 for example, detects an increase or decrease in currentconsumption by way of a voltage differential across both ends of thecurrent detector resistor 112. Therefore in the vehicular power supplydevice in Japanese Unexamined Patent Application Publication No.2010-81692 when the consumption current has dropped by approximately adouble-digit figure, there is nearly no difference between the voltagedifferential across both ends of the current detection resistor 112 andthe offset voltage on the differential amplifier 114, so that thedifferential amplifier 114 cannot correctly perform amplification. Thisstate reveals that the vehicular power supply device in JapaneseUnexamined Patent Application Publication No. 2010-81692 does notpossess a mechanism for equalizing the consumption current in low powerconsumption modes such as sleep mode. In other words, the vehicularpower supply device in Japanese Unexamined Patent ApplicationPublication No. 2010-81692 possesses the problem that the device isincapable of reducing voltage irregularities (variations) among thebattery cells caused by consumption current (such as leak current) insleep mode.

In contrast, the load current Iload in the voltage monitoring modulesVMM1-VMMn has a drop in sleep mode that is smaller than a two-digitfigure. In the voltage monitoring system of the first embodiment, whenthere is a large fluctuation in this type of load current, the operatingcurrent can be set smaller to match fluctuations in the load currentIload and in this way extend the life of the battery cell. This resultis obtained because in the voltage monitoring system of the firstembodiment the operating current of the voltage monitoring modules insleep mode is determined based on a preset sleep current code. So in thevoltage monitoring system of the first embodiment, the operating currentduring sleep mode can be set with greater accuracy than the case wheresetting the sleep mode operating current based on measurement results.In other words, the voltage monitoring system of the first embodiment iscapable of adjusting the operating current according to the drop inconsumption current during sleep mode and so battery consumption can belimited and the drive distance of the vehicle can be extended.

The voltage monitoring system of the first embodiment can furtherspecify the maximum value of the load current Iload from the loadcurrent Iload values acquired from all the voltage monitoring modulesduring startup of the voltage monitoring system or during the update(rewrite) processing of the normal current code. Therefore when there isdefinitely an abnormal current among the acquired operating currentmeasurement values, the voltage monitoring system of the firstembodiment can detect (identify) the defective voltage measurementmodule of that abnormal current measurement value by detecting thatapplicable abnormal current measurement value.

Second Embodiment

The second embodiment is described by utilizing an example that is avariation of the regulator circuit 11 and the adjusting current controlcircuit 12. FIG. 15 is a block diagram showing the regulator circuit 11a which is a modification or variation example of the regulator circuit11, and the adjusting current control circuit 12 a which is amodification or variation example of the adjusting current controlcircuit 12.

In the regulator circuit 11 a shown in FIG. 15 the output transistor P0of the regulator circuit 11 was substituted with an output transistor N1configured by a NMOS transistor.

Further in the adjusting current control circuit 12 a as shown in FIG.15, the PMOS transistor P1 of the adjusting current control circuit 12was substituted with a current mirror circuit configure by the PMOStransistors P3 and P4. The reference numeral 23 a was affixed to thecurrent setting circuit containing these PMOS transistors P3 and P4.

The source of the output transistor N1 is coupled to one end of thefirst resistor R1, the drain is coupled to the drain of the PMOStransistor P3, and the output signal of the first differential amplifieramp0 is supplied to the gate.

The source of the PMOS transistor P3 is coupled to the power supplyterminal VCC, and the drain and gate are coupled in common. The PMOStransistor P4 is coupled by a current mirror coupling to the PMOStransistor P3. A current setting resistor Ris is coupled between thedrain of the PMOS transistor P4 and ground terminal.

Even in this type of configuration, an output current Iout whose size isset based on the reference current Iref, flows in the output transistorN1. The relation between the output current Iout and the referencecurrent Iref is determined by the transistor size ratio of the PMOStransistors P3, P4. The operation of the regulator circuit 11 a and theadjusting current control circuit 12 a in the second embodiment is thesame as the regulator circuit 11 and the adjusting current controlcircuit 12 of the first embodiment so a description is omitted here.

The regulator circuit 11 a and the adjusting current control circuit 12a in the second embodiment are in other words presented as one exampleof a variation or modification of the regulator circuit 11 and theadjusting current control circuit 12. Other detailed variations areshown as configuration rendered in the normal course of work by oneskilled in the art.

Third Embodiment

FIG. 16 is a block diagram of the voltage monitoring system of the thirdembodiment. In the voltage monitoring system of the third embodiment asshown in FIG. 16 one cell monitoring unit CMU is coupled to one voltagemonitoring module. The cell monitoring unit CMU then communicates by wayof the respective insulation elements and the CAN interface with thebattery management unit BMU.

The cell monitoring unit CMU of the third embodiment is supplied withpower from the power supply circuit of the voltage monitoring module,and performs readout (or loading) instructions for measurement valuesfrom the voltage monitoring modules and instructions for generatingmeasurement values to the voltage monitoring modules. The cellmonitoring unit CMU also sends data acquired from the voltage monitoringmodules to the battery management unit BMU according to a request fromthe battery management unit BMU. The cell monitoring unit CMU of thethird embodiment is equivalent to the cell monitoring unit CMU of thefirst embodiment except for the arithmetic processing function foracquired data. The battery management unit BMU on the other handcontains a function for arithmetic processing of acquired data that wasperformed by the cell monitoring unit CMU of the first embodiment.

The voltage monitoring system of the third embodiment configured asdescribed above, includes a cell monitoring unit CMU in the load circuitsupplied with a load current output by the power supply circuit of thevoltage monitoring modules. In this case also, the operating current ofthe (plurality of) voltage monitoring modules can be equalized the sameas in the other embodiments by generating an normal current code andsleep current code by the battery management unit BMU.

In the voltage monitoring system of the third embodiment, the batterymanagement unit BMU in other words generates a normal current code. Thecircuit block for generating the normal current code can in other wordsbe changed as needed in whatever circuit block where included.

The present invention is not limited by the above described embodimentsand changes or modifications can be made as desired that do not departfrom the scope or spirit of the invention.

What is claimed is:
 1. A method of operating a voltage monitoring systemconfigured to monitor a voltage of a plurality of battery cells coupledin series, the voltage monitoring system comprising: a voltagemonitoring module including an adjusting current control circuit; and amodule control circuit configured to control the voltage monitoringmodule, the method comprising the steps of: (a) generating a firstoperating current setting command by a module control circuit; (b)generating an adjusting current in response to the first operatingcurrent setting command so that an operating current consumed in thevoltage monitoring module reaches a first value corresponding to thefirst operating current setting command; (c) generating an operatingcurrent switching command by the module control circuit; (d) haltinggenerating of the adjusting current in response to the operating currentswitching command; (e) generating an operating current measuring commandby the module control circuit; (f) measuring the operating current inresponse to the operating current measuring command; (g) generating asecond operating current setting command, by the module control circuit,based on the measured operating current; and (h) generating an adjustingcurrent, by the adjusting current control circuit, in response to thesecond operating current setting command so that the operating currentreaches a second value corresponding to the second operating currentsetting command.